Not Applicable.
As the current trend in offshore oil and gas production advances into deeper waters, and the oil and gas prices remain depressed, it is becoming increasingly necessary for the industry to develop cost effective solutions to develop small fields in deep waters.
A typical solution for such cases is to keep the production facilities on a xe2x80x9chost platformxe2x80x9d and connect the deep-water well(s) to the platform with pipelines and risers. The supporting equipment for the subsea tree control, such as hydraulic and electric power units, chemical injection pumps and tanks, and a control console, are also housed on the host platform. The subsea tree control is accomplished via long umbilical(s) consisting of electric conductors, hydraulic lines and chemical injection lines laid alongside the pipeline. In addition, two parallel pipelines are necessary to accomplish the roundtrip pigging operations. Obviously, the cost and technical challenges of this conventional tieback system increase as the tieback distance increases, and to a lesser extent as the water depth increases. For most cases, 20 miles represents the practical limit for the maximum tieback distance with the conventional tieback system. Hence, it is desired to provide a system that can provide greater tieback distances without the cost and technical disadvantages that heretofore have prevented increasing the tieback distance.
According to the present invention, a permanent low-cost multi-function surface support facility is provided that allows for several functions associated with well operation to be provided from a permanent local structure. According to a preferred embodiment, the permanent local structure comprises an unmanned mini-floating platform that supports equipment such as equipment for subsea tree control, hydraulic and electric power units, chemical injection pumps and tanks, and the associated control console(s). The present mini-floating platform is preferably positioned substantially directly over the subsea tree(s) and manifolds. Hence, the subsea tree is connected via a much shorter umbilical cable to the floating platform. The control for equipment on the mini-platform, including the power and chemical injection units, is preferably accomplished via a links to a remote host platform, such as microwave, satellite, radio, etc. The present mini-floating platform can also support a vertical access riser for well workover and/or pigging equipment for pipeline maintenance, and provides surface support for subsea production systems such as pumps, meters, separators etc.
The present invention eliminates the need for very long umbilical cables and the very long pipelines needed for pigging. Thus, cost savings are associated with the reduction in length of all but the production pipeline. The present novel approach to the production and control of subsea wells is accomplished by splitting the control and production requirements between a host facility and a local platform, allowing significant advantages and cost savings.